Immersed tube method-based tunnel construction is to respectively transport tunnel caissons, which are prefabricated in a semi-submerged barge or a dry dock, in a floating manner to preset positions for immersion and jointing. In order to successfully immerse the last tube section, a distance space longer than the tube section must be reserved, and the tube section immersed and jointed in the reserved distance space is regarded as a final joint. The final joint of the immersed tunnel is crucial for construction of the immersed tunnel, particularly for construction of an open sea ultra-long immersed tunnel under severe site construction conditions, and complicated ocean environmental conditions and weather conditions such as waves and ocean current.
At the present, constructed large-sized undersea immersed tunnels are mainly distributed in America, Europe and Japan. China has built several immersed tunnels, but has not yet built large-sized undersea immersed tunnel. Moreover, the domestic deep-sea or cross-sea immersed tunnels are planned or under construction. It is a severe challenge for construction of the final joint of the immersed tunnel because of different geographical environments, hydrology-weather conditions, construction technologies and construction period requirements.
General schemes for final joints of open sea large-sized immersed tunnels in the world mainly include: conventional weir enclosing method and water stop plate method, and modern end portion block method, V-shaped block method and KEY tube section method, wherein the weir enclosing method and the end block method are applicable to a situation that the final joint is placed at a shoreside hidden section; the V-shaped block method has high requirements for measurement precision and jointing deviation; in the KEY tube section method, it is required that a tube section is generally 100 m in length, and if the tube section is too long, its installation and control would hardly meet a precision requirement of the construction method; and in the water stop plate method, underwater work is mainly completed by diving, and the construction period for river immersion is generally 3 to 4 months. For the open sea large-sized immersed tunnels, diving work is limited by weather and wave current conditions of the open sea; and in addition, due to the mutual effect of uncertainty of the open sea site working time and a back-silting environment, the construction period and the quality of a project and a project risk are hard to control.
Therefore, in view of the above problems, the present application is in urgent need of a novel scheme for the final joint of the immersed tunnel, which may make the installation construction of the final joint faster and safer in a project with a construction site far away from the land, difficult open sea working conditions and a relatively high requirement for the construction period, thereby shortening the project construction period and lowering the quality risk